Interaction of genetic and environmental controls over the production of antibody will be studied, especially as regards the influence of neonatal exposure to environmental antigen on the development of salivary antibody. The model used will be the Harvard inbred caries-resistant (CR) and caries-susceptible (CS) strains of rats and their responses to injected, killed streptococci or to oral and gastrointestinal association with the cariogenic bacteria. This will be an extension of previous observations that CR rats born in a streptococcus monoassociated isolator showed decreased immune response and caries resistance. These second generation gnotobiotic CR rats differed from their parents only in high levels of maternal antibody and earlier exposures to living bacterial antigen. By experimental analyses of immune responses and dental caries resistance of rats under various neonatal environments, we will be able to identify a factor affecting antibody production stimulated by enteric bacteria and investigate further the correlation between this antibody and dental caries incidence. In addition, we will explore the parameters of the apparent "high and low responder" genetic difference in immune response between CR and CS monoassociated rats that we have found in previous experiments. This knowledge could be applied to genetic factors influencing the caries-free human. It will contribute to understanding of local antibody formation, consequences of local administration of antigens and possible protective functions of secretory antibody.